1. Eng. Yasser Bayoumy
MSc. of Maritime Energy Management - WMU – Sweden
Lecturer in the Maritime Upgrading Studies Institute – MUSI
Chief Engineer
Automatic Control Fundamentals
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Control theory
A control system is an interconnection of components forming a system configuration that
will provide a desired system response.
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Closed-Loop Control System
A feedback control system is a control system that tends to maintain a prescribed relationship
of one system variable to another by comparing functions of these variables and using the
difference as a means of control.
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Proportional Control
The action of this particular
controller is direct, since an increase
in process variable signal (pressure)
results in an increase in output
signal (pressure).
To reverse the action ……..?
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Proportional Derivative Control
Derivative action causes the output
pressure to shift either up or down
(depending on the direction of input
change) more than it would with just
proportional action alone in
response to a ramping input.
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Proportional Integral Control
Derivative action causes the output
pressure to shift either up or down
(depending on the direction of input
change) more than it would with just
proportional action alone in
response to a ramping input.
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PID Control
The terms gain K, derivative time Td, integral time
Ti which can be set by beam pivot point and two
bleed valves. This is a combination of all the three
controllers described above. Hence it combines
the advantages of all three. A derivative control
valve is added to delay the response at feedback
bellow. Addition of derivative term makes the
control system to change the control output
quickly when SP and PV are changing quickly.
This makes the system more stable.
24. 1
2
1
2
A
B
C
𝐴1
𝐵1
𝐶1
Variable
displacement
pump
From Telemotor
Control
Connection to Rudder
stock or Tiller
Fulcrum
1
1
2
2
𝐵2
Follow-up control (Floating lever)
1. The telemotor moves the end of floating lever A to 𝐴1 for
a certain rudder angle ( certain direction and angle)
2. Subsequently, The pump control is moved, therefore
from B to 𝐵1. Pumping of the hydraulic oil causes
movement of the rams and the end of rod C moves to 𝐶1 ,
thus causing the pump control to be pulled back to the
neutral position B.
3. If the rudder is displaced by a heavy sea through lifting
of the relief valves, the hunting gear is moved by the
rudder stock. This will put the pump on stroke and
rudder will be restored to its previous position.
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S/G Modes
Normal Procedure
(From Wheel House)
Non-Follow Up Mode Follow Up Mode
Manual Method (wheel) Automatic Steering Gear
Emergency Procedure
(From S/G Compartment)
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S/G Modes
Follow Up Mode
• This is the Principal mode of steering.
• In this mode, the rudder Follows the wheel. If the rudder is put 10° to Starboard, the rudder will
follow to 10° to Stbd and remain there as long as wheel is kept to 10° to Stbd.
• To bring the rudder to ‘Midship’, the wheel will have to be brought to ‘Midship’.
• This mode is followed in the following methods of steering
The hand steering mode in which the steering wheel sets the rudder angle,
Auto-steering mode in which the wheel order is automatically generated depending upon the
difference between the ordered course and the actual course
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S/G Modes
Non-Follow Up Mode
• This mode of steering is not done with a steering wheel but with a NFU
Lever.
• The NFU lever does not have any markings. As long as it is kept pressed, the
rudder will continue turning and stop the moment the lever is released.
• This mode is used when ships telemotor system fails. In that case, the NFU
lever sends rudder setting directly to the Control Unit.
• To return the rudder to the midship, the NFU lever will have to be pressed to
the opposite side of the initial movement and kept pressed till the rudder is
midship.
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S/G System
Pressure
Relief Vv.
Filter F
Solenoid
Control Valve
Shock and Bye-Pass
Valve
Steering Gear
Cylinders
Rudder cross Head
Tie Bar
Pump
Tank
By-Pass
Vvs
Actuator isolating Vvs
• The Pump takes a suction from the Tank and discharges through a
Filter to a Solenoid Operated Control Valve.
• The Control Valve has two sets of ports:
1. One supply line to one side of each ram.
2. Other side is the return line back to the tank.
• A Shock And Bye-pass Valve is fitted to prevent damage to the
system in the event that the rudders are suddenly forced to go in the
wrong direction due to hitting an underwater object.
• Relief Valve relieves the oil directly back to the tank when there is
no demand for oil (the rudder is not moving), This allows the pump
to be a continuously running
